According to business magazine Forbes, Winfrey, whose 21-year-old talk show 'Oprah' is watched by 30m viewers each week, is believed to have earned $225m (£123m) over the last 12 months.
'Braveheart' actor Mel Gibson came third in the Celebrity 100 list, behind golfer Tiger Woods, who has won 60 golf tournaments in the last 10 years.
'Star Wars' creator George Lucas returns at four after a one-year absence, but is first in the money rankings with estimated earnings of $290m (£159m) from his money-spinning saga.
At nine, singer Sir Elton John is the highest-ranking Briton, with estimated earnings of $44m. He recently extended his Las Vegas show 'The Red Piano' at Caesars Palace until 2008. Last year, it pulled in $40m.
Other UK celebrities include Harry Potter author JK Rowling at 22, singer Rod Stewart at 32 and supermodel Kate Moss at 93.
Newcomers to the list include the cast of 'Desperate Housewives' including former Bond girl Terri Hatcher at 25 and 'Elf' and 'Starsky and Hutch' star Will Ferrell, whose $40m (£22m) earnings make him the list's second most successful actor, behind Tom Cruise at number 10.
Actor Jim Carrey and Tom Hanks and veteran rockers the Rolling Stones, ranked fifth last year thanks to their successful world tour, did not make it into the list.
Forbes rates celebrities' influence according to press coverage, internet presence and estimated earnings between June 2004 and June 2005.
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